1. Field of the Invention
The present invention relates to a display circuit best suited to the line-scan-control of a liquid crystal (LCD) panel.
2. Description of the Prior Art
Liquid crystal display panels have been conveniently used in electronic timepieces and portable word processors, etc. because they can be operated with extremely low power consumption and provide a flat screen. The LCD panels are generally operated with AC driving signals, because DC voltages shorten the effective operational life of the LCD panel.
In an AC driving operation, a plurality of different DC bias voltages are selected with reference to scanning data and display data to produce AC driving signals which are supplied to the X and Y electrodes of the LCD panel. For example, when a voltage difference between the X and Y electrodes of an LCD panel of the nematic type exceeds a threshold voltage, it will disorient the molecular orientation of the liquid crystal layer, thus resulting in a display or lighting condition. On the other hand, when the voltage difference is less than the threshold value, it orients the liquid crystal molecules in the vertical direction, thus resulting in the non-display condition.
In the conventional display circuit, in order to place all of the display cells of the LCD panel in their non-active condition, a voltage having a value which does not exceed the threshold value is supplied between the X and Y electrodes of each of the display cells. However, this is disadvantageous in that since an AC signal less than the threshold value is supplied to each of the X and Y electrodes in the LCD panel, a discharging or charging current flows through the equivalent capacitance of the display cells, thus increasing the operational power consumption.